The most self-incriminating thing a suspect can say to a law enforcement official.
A suspect who has a substantial amount of evidence linking him/her to a crime
will act completely oblivious to the matter.
Saying such a phrase
will destroy a suspect's credibility since he/she is being
non-cooperative and is obviously lying.
Officer: We've got your
DNA on the dead body, your fingerprints are all over the murder
weapon, and we have three credible eye-witnesses saying they saw you pull the
trigger!
Suspect: I have no idea what you're talking about.
Officer: Thanks, that's all I needed to hear.